That's pretty normal for hiring PhDs in my practical experience. My first job was 'senior' and it's the same for everyone else I can think of. You are senior - you've been part of the community for around four years by that point and by graduation you're probably part of several committees and starting to mentor others. Why isn't that 'senior'?

Not the case in my field - biomedical. The hiring manager at a large pharmaceutical company told an audience of postdocs & graduate students at a career event a few weeks ago that they prefer to see a postdoc of at least 2-4 years to be considered for a senior scientist position.

Whether you have senior in your title is just nomenclature at pharma companies. Plenty do have it in your title just after PhD, reserving Scientist roles for those coming out of BS who are doing grunt work. That said, other companies have those as “technician” and PhD (maybe masters) is start of Scientist.

Getting hung up on title in Pharma is not a good move. It isn’t uniform at all.

I agree that nomenclature is just jargon. There's also the context of the parent, that senior jobs are typically available right out of university. I do not know the field the parent is in, though. In my experience of the biomedical field, this isn't the case. I'm a postdoc at a good medical school in the US, and most of the postdocs I've interacted with would happily take an industry job if they could manage it - there just aren't enough jobs to go around. The prospects for fresh Phds are even more grim.

Worked pretty smoothly for me. Probably helped that I had some relatively good looking private sector consulting gigs during my doctorate and post doc.